Polymerization of gases



YPatented Oct. 15, 1935 UNITED STATES PATENT? OFFICE f 2,011,325 Y roLYMEarzA'rroN or GASES Robert F. Ruthrui, Hammond, Ind., assignor to Standard Oil Company, Chicago', Ill., a corporation of Indiana {ir-:Psw Application' August 24, 1932, Serial No. 630,282 i My invention relates to an improved process for obtaining `low boiling liquid products by the polymerization of olenic gases. y

\ It is well known that olenic gases can be polymerized at'elevated temperatures and pressures to yield low boiling liquid products. These olenic gases may be produced by high temperature cracking of saturated or parailinic gases. Furthermore, such polymerization systems and such 1o cracking systems may be advantageously operated in'combination with each other as is disclosed in co-pending application, Sullivan and Ruthrui, Serial No. 577,226. In the Sullivan and' Ruthruft process cracked gases are scrubbed with oil at elevated pressures, undissolved methane,l.y

2:5 aration between the scrubbing mediumand dissolved gases, and also the separation between liquid polymerization products and dissolved unreacted gases, in a plurality of stages subsequent to an initial high pressure separation and removal of undissolved xed gases, certain gas fractions of unexpectedly high olefin content may be obtained and may be so combinedand recycled as to considerably increase the olen content of the gas charged to the polymerization system. Brieily described, the operation of my system is as follows:

Considering rst the polymerization system, olenic gases are polymerized in a suitable heater with or without a soaking drum at temperatures above 750 F. and ordinarily of 850-1000 F. and pressures o f 50G-3000 pounds, the reaction time being from 0.5 to 20 minutes, and ordinarily from 1-10 minutes. Subsequent to this step all gases and products are cooled and fixed gases are separated at substantially full reaction pressure. The pressure on the liquid .products and dissolved gases from the high pressure separator is released in two or more stages. Varying proportions of the' gas released from the several stages are recycled to the polymerization step. 'I may, for example, (subsequent to the initial high pressure step) first separate a gas of low oleinA content and then one of high olefin content, the rst separated gas being eliminated from the system and the second -recycled. On the other hand, I may use more relatively low pressures.

vcentrated olen gases `than two separation steps and also I may recyclev varying proportions ofthe gases from the several stages instead of completely eliminating any one stream from the system.

The number of stages used, the exact pressure 5 maintained in each, and the composition and disposition of the gas released in each stage (i. e. whether recycled or eliminated) will, of course, depend on the composition of the unreacted gases leaving the polymerization step, which', in turn, 10 will depend on the composition ofthe fresh olen gases fed to the system and on the exact conditions maintained therein.

I may also operate my process in conjunction with a gas cracking step. In this case saturated 15 gases are cracked at elevated temperatures a-nd The resulting low olefin content gas is cooled and scrubbed under higher pressures, the xed gases are eliminated, the

I scrubbing oil and -dissolved gases are separated 20 stepwise in a plurality of stages and gases are,l removed from each stage. The gas separated from each stage is. controllably (l) recycled to the cracking step, (2) delivered to the polymerization system, and (3)!divided between (l) and (2) In 25 determined proportion so as to establish optimum ultimate yield conditions. y

When my polymerization system is operated in conjunction with a gas-cracking system, low olefin content gases separated In oneA or more 30 of the plurality ofv gas-product separators following the high pressure separator of the polymerization system are not discarded, but are returned to the gas-cracking step.

Suitable apparatus for carrying out my process 35 is shown diagrammatically in the attached drawing which represents an elevationalvi'ew thereof, and which forms part of this specication.

The operation of my process in detail is as follows: i 40 a Referring to the drawing andv considering ilrst the polymerization system alone. Relatively concontaining over 50% of gaseous oleflns enter-through line I0 and are compressed by pump II to 50G-3000 pounds per 45 square inch and introduced into the heating' coils of heater I2, wherein the gases are heated to '750-1000 F. Heater I2 may contain preheating and soaking coils in which thereactions are completed, or it may function solely as a preheater 50 in which case valve I3 in exit line I4 is closed, valves I5 and I6 are opened, whereby the polymerization reactions are permitted to complete themselves in soaking chamber I1. In either Case, all gases and productsare cooled in cooler atelseparator 24. Gasesmay be removed from' separator 24, through valve.25, pump 26 and line 21 for recycling to the polymerization step, or may be wholly or partly vented from the system through valve 29. Liquids and remaining dissolved gases are removed through valve 29 and line 30, wherein the pressure is further reduced and are introduced into low pressure separator 3| from which essentially gas-free products are withdrawn through 32, while gases, may be recycled throughl 33 or wholly or partly vented from the system through 34.

As previously stated I may operate my system in con-junction with a gas-cracking system, in fact, I may can'y out the entire operation starting with essentially saturated or parafilnic gases.

Referring again to the drawing, if this set-up be used, predominantly saturated gases enter through line 35 and are cracked at temperatures of 1300-1750 F. and 0 to 100,1bs. per square inch pressure above atmospheric or thereabouts in heater 36, from which these gases either pass through valve 31, soaking chamber 39 and valve 39, or may be passed through valves 40, by-pass 4I and valve 42. In either case the gases are essentially completely cooled in cooler 43, following which'any liquid condensates may be drawn oi through 44 prior to compression of the g'ases j by pump 45 and injection of said compressed gases into scrubber 46. In the scrubber 46 the gases which have an oleiin content of not over 50% by volume (and ordinarily of less than 40% oleiins by volume) are contacted with a suitable scrubbing oil whereby oleiinic hydrocarbons (and to a somewhat lesser extent the satrated hydrocarbons havingztwo or more carbon atoms) are dissolved. Fixed gases, such as hydrogen or methane, are eliminated through 41, cool scrubbing oil being introduced through line 49, while enriched oil is withdrawn through 49 and valve 50, passed through -interchangerl or heater 5I and introduced into intermediate'separator 52.

Separator 52 may be equipped with suitable heating means 53 at a low point therein and may be provided with cooling means 54 at an upper point therein. Gases driven oiilr in 52 are withdrawn through line 55, while the liquid and still remain- Aing dissolved gases are-withdrawn through 56 and valve 51, passed through heat interchanger or heater 59 and enter separator 59 which likewise may be provided with heating means 60 and cooling means 6I. Gases driven oil in this separator are removed thru line 62, while stripped scrubbing oil is removed through valve 63 and-line my process I use two separation steps subsequent to the initial separation of iixed gases, both in the polymerization system and in the oleiin gas concentration system. In this case essentially all of the gas from the iirst separator or separators is 5 merization -product separators, I do not limit'l5 myself tol this arrangement but may use stepwise reheating in either or both systems, or stepwise pressure reduction in either or both systems. I may, however, use more than two intermediate separators following the high pressure sepa- 20 rator 20 or scrubber 46. The distribution of gases from each separator between inlet 35 to .the cracking system or inlet I0 of the polymerization system will be so determined as to give the optimum concentration of olen gas-entering the 25 polymerization. system and will be dependent upon the composition of the original gas fed to the cracking or polymerization step through line 35 or line I0, on the exact conditions maintained during the cracking and polymerization steps 30 and on the exact conditions maintained in the scrubber 46 and separator 20 and the separators following thereafter.

If my polymerization system be so operated in conjunction with a gas cracking system, instead 35 of eliminating from the system gases from sepa- `rators 24 or 3| of the polymerization system through vents 29 or 34.respectively. any gases from these' separators that are not desirable for recycling to the polymerizing step through line 21 40 will be drawn oil. through 1I and 12 respectively, and passed through line 13 to inlet 35 of the gas cracking step.

I may also under certain conditions prefer to I operate my polymerization step in the presence oi 45 certain amounts of liquid oil. In such case I may draw olf regulated portions of scrubbing oil containing dissolved oleiins from separators 46 and/or 52 through valves 14 and 15 respectively and inject said materials by pump 16 through 50 line v'I1 into the inlet I6 to the polymerization heater I2.

I may also operate my polymerization system in conjunction with the olefin concentration system represented by 45 to 69 but without the gas 55 cracking system 35-44. In this case I mayoperate on low oleiin content gases obtained or produced from any suitable source which are introduced through line 19 and valve 19 into the intake of pump 45. In this case the operation o! all 00 other parts of my system is as previously described. It will also be evident that the `olefin concentration system 45-69 may be operated independently in order to produce a rich olefin gas for any purpose from lean olefin gas from any 65 source.

If I operate my polymerization system in conjunction with the cracking system and make use of -three or more separators in my olen concentration system 45-66, then I may under certain 70 circumstances make use of only two stages of separation between polymerization products and unreacted gases from the polymerization system. In this case I open valve 60 and close valves 23, 25, 29, and 1I, thereby eliminating the inter- 75 above 2,000 lbs. I may mediate separator 2l. All other details 'of operation of my system will reinain as previously described.

IfI operate my polymerization system in ,conjunction with the olen concentration system to 6,8, but without the gas cracking system, I may make use of line 8l and Valve 82 whereby I may divert gas released from one or more of the separators 26, 3l, etc. back to the olefin concentra.-

tion step.

Altho as previously stated I do not limit myself to the use of only two intermediate separators subsequent to the initial fixed gas separator, I prefer to useonly two such separators. I also prefer to select my starting materials and to operate my polymerization and/or cracking systems and my separators so that an olenic gas is separated inthe rst intermediate separator and a low olen content gas in the second intermediate separator. This type of operation has` the added advantage that the olefinic gas which is to be recycled to the high pressure polymerization system is in all cases obtained or recovered at the highest possible pressure, whereby considerable operating economies are realized.

It will be understood that scrubber 46 and separator 20, 24, 3|. 52. and 59 may be provided with bubble or baille plates and/or anyA other conventional means for improving scrubbing or separations respectively therein. Wherever the term substantially full reaction pressure? is used herein or in the claims hereof with resp'ect to the operating conditions o f high pressure separator 20, this is to be understood as being vsubject to the qualication that frequently it is preferable not to operate the said separator at pressures above 2,000 lbs. per square inch since at the ternperatures attainable with ordinary cooling water, separation of phases is frequently not satisfactory at higherpressures than this. In case, therefore, that I make use of reaction pressures of reduce pressure. to at least that point by valve I9 prior to high-pressure separator 20.,

By low olen content gasesj, where this term 'is used herein, I refer to gases having olefin contents of less than and ordinarily of more than 20%. By predominatingly saturated gases,

such as I may use as charging material for the high temperature gas cracking step,.I refer to gases containing 20% or less of gaseous olefins or containing none thereof. By oleiinic gases o r olefinic gas I refer to gases having an olen content of 50% or more and preferably of more than such as may be obtained by the concentration steps described herein or may be obtained from other sources.

The foregoing being a full andcomplete description of my invention:

1. In a process forvthe polymerization of oleilnic gases at temperatures of 7501000 F. and under pressures of 50G-3000 lbs. per sq. in., the steps of y separating liquid products from unreacted gases in at least three stages at progressively lower pressures, separating xed gases from .products in the rst stage, eliminating xed gases from the system, separating olenic gas from at least one stage subsequent to the first stage and rev cycling substantially all of said gas directly to the polymerization step, and eliminating the predominatingly saturated gases separated in the other stages from the system.

2. In a process for the polymerization of olenic gases at temperatures of 750-1000 F. and under l ing olenic gas from pressures of 50G-3000 lbs; per sq. in., the steps of separating fixed gases from products at substantially full reaction pressure and relatively low temperature and eliminating said fixed gases from the system, separating remaining gases from iiquid products in at least two subsequent stages at progressively lower pressures, separating oleiinic gas from at least one stage and recycling' substantially all-'of said gas directly to the polymerization step, and eliminating the pre- 10 dominatingly saturated gases separated in the other stages from the system.

3. In a process for the polymerization of olenic gases at temperatures of '750-l000" F. and under pressures of 50G-3000 lbs. per sq. in., the steps oi separating lliquid products from unreacted gases in at least three stages at progressively lower pressures, eliminating substantially all gasesfrom the first stage from the system, recycling oleiinic gases from at least one stage directly to the polymerization step, subjecting predominatingly saturated' gases from at least one stagey to cracking at 1300l750 F. tor obtain additional olefinic gases therefrom, and returning said olenic gases to the polymerization step.

4. In a process for the polymerization of oleiinic gases at temperatures of '750-l000 F. and under pressures of 500-3000 lbs. sq in., the steps of separating liquid products from unreacted gases in three stages wherein the ilrst stage is at substantially full reaction pressure and relatively low temperature andthe subsequent stages-.are at progressively lower pressures, eliminating fixed -gases from said first separating stage from the system, recycling olefinic gases from the second 35 i 5. In a process for the polymerization of ole- 40 `iinic gases at temperatures f 'l50-1000 F. and 'under pressures of 50G-3000 lbs. per sq. in.,A the steps of separating liquid products from unreacted gases in three stages wherein the rst stage is at substantially full reaction pressure and rela- 45 tivelylow temperature and the-subsequent stages are at progressively lower pressures, eliminating fixed gases from said iirst stagev from the system, recycling olenic gases from the second stage directlyto ythe polymerization step, subjecting predominatingly saturated gases from the third separating` stage to cracking at I300-1750" F. to obtain additional olefinic gases therefrom, and returning said olenic gases to the polymerization step. Y D 6. In a process for the production, of liquid products from low olen content gases, 4the steps of scrubbing said gases with oil at elevated pressure, eliminating undissolved'gases separating dissolved gases from the oil in at least two subsequent 6D I 'stages at progressively lower pressures, recoveryseparating oleilnic at least one of said stages, polymerizing .said olefinic-gas to liquid productsv at temperaturesof 750-1000 F. and under pressures of 500-3000 lbs". per sq. in., separating said 6o liquid products from unreacted gases in at least three stages wherein the first stage is at substantially full reaction pressure and at relatively low temperature and the subsequent stages are at progressively lower pressures, eliminating undissolved fixed gasesifrom the first separating stage from 'the system, separating dissolved gases-,from liquid products in at least two subsequent stages, 'gas from at least one of said stages, recycling said gas directly to the polymer- 75 ization step, and separating low olen content gas from at least one of said stages and returning said 'gas to the oil scrubberof the olefin concentration step.

7. In a process for the production of liquid products/ from predomina-tingly saturated gases, the steps of crackingl said gases -at temperatures of I300-750 F., scrubbing cracked gases with oil at elevated pressures, 'eliminating undissolvedl gases, separating dissolved gases from scrubbing at progressively lower pressures, eliminating.

gases separated in the rst stage from the system, recycling oleiinic gas' separated from at least one stage directly to the polymerization step, and recycling predominatingly. saturated gases separated from at least one stage directly to the rst named gas cracking step.

8. In a process for the production vo1' liquid products from low olen content gases, the steps of scrubbing said gases with oil at elevated pres# sure, eliminating .undissolved iixed gases, recoveringolefinic gas'in a second separating stage, polymerizing said oleni'c gas to liquid products' at temperatures of 750-1000" F. and under pres- :ures of 5 00-3000 lbs. per sq.`in., separating said liquid products from. unreacted gases in three stages wherein the rst stage is at substantially full reaction pressure and at relatively low tem- .perature and subsequent stages are at progressively lower pressures, eliminating ilxed'gases 5 from the first separation stage from the system, separating A.olenic gas from the second stage, recycling said gas directly to the polymerization step, separating low ulen content gas from the third stage, and returning said gas to the oil 10 scrubber of the dle'n' -concentration step. 9. In a process for the productionvof. liquid products from predominatinglysaturated gases, the steps of cracking said gases at temperatures of 1300 l750 F., scrubbing cracked gases with oil 15 at elevated pressures, eliminating undissolved gases, separating dissolved gases from scrubbing oil intwo stages at progressively lower pressures, recovering olefinic gas -from the iirst stage, recy- `cling predominatlngly saturated gases fromvthe 20 second stage directly to the c iracking step, polymerizing aforesaid' olenic gas at temperatures of 750-1000 F. and under pressures of 50G-3000 lbs. per sq. in., separating unreacted gases from liquid products in three stages wherein the first 25 is at substantially full reaction pressure and relatively low temperature and subsequent stages are at progressively lower pressures, eliminating xed gases separatedjn the ilrst stage from the system, recycling oleiinic separated in the 30 second stage directly to the polymerization step, andrecycling gases 'separated .in the third stage directly to the first-named gas cracking step.

ROBERT F. RUTHRUFE. 

